Gas inlet structure for combustion chambers



March 11, 1958 f P: F; AsHwooD GAS INLET STRUCTURE FOR COMBUSTIONCHAMBERS Original Filed Dec. 25, 1947 Attorney;

Tdiifection flow of reactants in the chamber. is, open at both ends tocommunicate on one handwith .GAS INLET STRUCTURE FOR COMBUSTION CHAMBERSi 2,826,039 'i at ented Mar. 11,1958

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'12 In this way the approaching combustion reactants impinge not onthe'surface of the channel member itself but on an insulating layer ofrelatively cool combustionsupporting gas, whichlayer is constituted notby a small Peter Frederick Ashwood, Farnham, England, assiguor to PowerJets (Research and Development) Limited,

London, England, a British company Original application 1 December 23,-1947, Serial No.

7 793,375, now Patent No. 2,667,033, datedJanuary26, 1954. Divided andthis application May 28,1953, Serial No. 357,999

- 4 Claims. (Cl. 60-39-65) This invention relates to an improvedapparatus for the combustion of fuel in a combustion-supporting gas.

An object of the invention is to provide for the continuous combustionof large quantities of fuel in a comparatively confined space such asmay be required for combustion gas turbines.

Such combustion apparatus comprises normally a combustion chamber atleast partly enclosed in a duct conveying the combustion-supporting gas.A proportion of this gas andthe fuel are introduced into the chamber atone region thereof and reaction takes place as they proceed ultimatelyto the chaming along the channel.

proportion but by substantially the whole of the gas flow- It mightappear at first sight that the "upstreamwardly directed edges of thesides of the channel member would be inadequately insulated as comparedwith other surfaces but the impact of the her outlet, further quantitiesof combustion-supporting gas being admitted meanwhile to the chamber tomaintain the reaction or dilute the reaction products or both.

, It has been proposed, with a view to introducing suchfurtherquantities of gas to an interior region of the space defined bythe combustion chamber, to provide a gas tube, attached to the chamberwall and extending generally normally thereto and transversely to thelocal The tube the duct space outside the chamber, and on the other handwith said interior region of the combustion space.

in practiceit isfound that such gas tubes, being impinged on one sidealong at least a part of their length by the combustion reactants in thechamber, are subject to severe damage and are frequently largely burntaway notwithstanding that they are made of materials comparativelyhighly resistant to combustion conditions and that a considerablecooling effect is derived from the relatively cool gas flowing in thetube. With a view to mitigating this difficulty it has further beenproposed to provide a gas tube, either extending between opposite wallsof the combustion chamber as a cross-tube or projecting from one wall asa stub-tube, which is perforated along at least a part of its length toprovide apertures facing in the general direction from which thecombustion reactants approach the tube. By appropriate adjustment ofpressures inside and outside the tube it is supposed that a proportionof relatively cool gas forms a layer over the external surface of thetube serving to insulate that surface from, or to occlude from directcontact with that surface, the impinging reactants. In practice howeverit is found that this refinement does not effectively overcome thetendency to burning away of the tube.

A further object of the present invention is accordingly to provide amore durable means for conveying gas to an interior region of thecombustion space. According to the invention there is provided a channelmember extending from the chamber wall towards the interior region sothat the open side of the channel faces in the general direction fromwhich the combustion reactants in the chamber approach the member, thechamber being apertured to direct a flow of combustionsupporting gasinto the channel.

impinging reactants on the cool gas flowing in the channel apparentlycauses a continuous spilling of that gas over the channel edges wherebythey are insulated. It is further proposed with a view to supplementingthis effect that the channel be progressively reduced in transverse areain the direction away from the chamber wall to which it is attached. Onthe other hand, in case the natural tendency to spilling of thechannelled gas should be excessive, it is proposed that it be reduced tosome extent by inclining the channel member, inwardly of its point ofattachment to the chamber wall, in the direction of flow of theimpinging stream of reactants. It is considered that a constructionembodying both of these features will lead to a more controlled spillingof the channelled gas flow than would otherwise be the case.

An example ofsuch a construction is illustrated in the accompanyingdrawing which represents the combustion apparatus in longitudinalsection.

- Referring to the drawing, the combustion apparatus comprises an airduct, 1 having at its upstream end a flange 2 by which it is intendedthat it should be secured directto the outlet from acompressor in a gasturbine of conventional type. The opposite or downstream end of the airduct has a flange 3 by which it is intended to be secured to the nozzlehousing of a turbine. A general arrangement of this character is ofcourse well known and so is not considered to require furtherdescription. Within the air duct is a combustion chamber .in the form ofa flame tube 4 having its upstream end .formed by a conical baffle 5with. its apex pointing downstream.

Inside the flame tube a fuel nozzle 6 is arranged in alignment with theapex of the conical baffle 5 to inject fuel in an upstream directioninto the upstream limiting region of the flame tube 4. The conicalbaffle 5 is mounted on a frusto-conical part 7 of the flame tube 4 whichforms in efiect an outward and downstream extension from the base of thecone, but also forms a lip 8 extending some distance upstream beyond thebase of the cone to form an aperture 9 dimensioned to admit a desiredproportion of the total air flow to the interior of the cone, theproportion in the preferred ease illustrated being a minor proportionwhich *is in the nature of a pilot flow. The flame tube is so arrangedthat the plane of its entry 9 is close up to that of the flange 2. Theair duct, except for a short cylindrical part immediately downstream ofthe compressor at 10, also increases in diameter in the downstreamdirection so as to form with the frusto-conical nose 7 of the flame tubean annular space 11 of increasing cross sectional area in the downstreamdirection designed as a diffusion passage suitable for the velocityconditions involved. From the downstream end of the annular diffusionpassage 11 so formed both the flame tube and the air duct are ofcylindrical form for some distance, the air duct terminating at itsdownstream end in a tapering section 12 leading to the turbine inlet.Upstream of this region the flame tube has an outwardly flaredfrusto-conical portion 13 which increases in diameter nearly to that ofthe air casing, the downstream end of this part being radially locatedby spaced peripheral projections 13a engaging the wall of the air duct.A small amount of air leakage is thus allowed between,

the flared portion 13 and the air duct, to prevent overheating efiects.The fuel pipes 14 for the nozzle 6 are screened from the air flow by anenclosing fairing 15.

The conical baffle forms a diffuser for air entering at 9 and has atleast one port or set of ports 16 at or near its apex in order tointroduce to a radially inner region at the base of the fuel jet orspray a pilot supply of combustion air insuflicient to cause reversalthereof while, further ports 17, 18, respectively are provided atintervals towards the base of the cone to provide a pilot supply of airto a radially inner intermediate region of the jet or spray and also tothe radially outer part of the fuel jet spray at a region where flowreversal thereof will take place in use due to the air flow.

The major primary supply of combustion air enters through a set of ports19 at or near the outlet from the annular dififusion passage 11 (that isat about the shoulder of the flame tube); this supply of air, it will benoted, is so arranged in the region of the fuel jet or spray as tointroduce air enveloping the latter somewhat downstream of its region offlow reversal. Further sets of ports 20, 21 for the inlet of secondarycombustion air and a cooling or diluent air respectively are provided atspaced downstream zones of the combustion chamber.

The flared portion 13 of the flame tube has a circumferentially spacedset of rectangular apertures 23-each of which coincides with the outerend of a channelled scoop 22 attached to the flame tube portion 13. Eachscoop extends inwardly and rearwardly of the flame tube from its pointof attachment and serves to convey diluent air from the associatedrectangular aperture to the central region of the flame tube. The openside of the channel of each scoop faces directly in the upstreamdirection and the side walls of the channel taper'and converge from theattached end of the scoop with a consequential reduction in transversearea of the channel.

This application is a division of application Serial No. 793,375 filedDecember 23, 1947, now Patent No. 2,667,033, issued January 26, 1954.

What I claim is:

1. Combustion apparatus having a duct for conveying acombustion-supporting gas, a wall combustion chamber at least partlyenclosed by said duct and apertured to admit a portion of thecombustion-supporting gas to one region of the chamber, means forintroducing fuel to said region of the chamber to react with saidportion of combustion-supporting gas, said chamber defining a flow pathfor the combustion reactants and having an outlet to which thecombustion reactants flow during reaction, and an elongated channelmember extending from the chamber wall inwardly across said combustionreaction flow path, said member being channelled in transverse sectionthroughout its entire length and arranged with the open side of thechannel facing upstream towards the approaching combustion reactants,said channel member having an open end facing into said chamber in adirection transverse to the direction of flow, said chamber beingfurther apertured to direct a further portion of combustion-supportinggas into said channel.

2. Combustion apparatus according to claim 1, wherein said channelmember is so shaped that the transverse area of the channel isprogressively reduced in the direction longitudinally of the member awayfrom the chamber wall from which it extends.

3. Combustion apparatus according to claim 2, wherein said elongatedchannel member is inclined, away from the chamber wall from which itextends, in the direction of flow of the approaching combustionreactants.

4. Combustion apparatus according to claim 1, wherein said elongatedchannel member is inclined away from the chamber wall from which itextends, in the direction of flow of the approaching combustionreactants.

References Cited in the file of this patent UNITED STATES PATENTS2,446,059 Peterson et al July 27, 1948 2,448,561 Way Sept. 7, 19482,531,810 Fyffe Nov. 28, 1950 2,541,171 McGarry Feb. 13, 1951 2,546,432Darling Mar. 27, 1951 2,601,000 Nerad June 17, 1952 2,610,467 Miller -cSept. 16, 1952 FOREIGN PATENTS 578,764 Great Britain July 11, 1946

